Atlanta - The second wintry storm in two weeks to hit the normally warm US south encrusted the region in ice Wednesday, knocking out electricity to hundreds of thousands of homes and businesses. It then pushed toward the heavily populated Northeast.
At least 11 deaths across the region were blamed on the treacherous weather, including three people who were killed when an ambulance careened off an icy Texas road and caught fire.
Nearly 3 300 airline flights nationwide were cancelled.
In an warning issued early on Wednesday, National Weather Service called the storm "catastrophic ... crippling ... paralysing ... choose your adjective."
Forecasters warned of more than 2.5cm of ice possible in places. Snow was forecast overnight, with up to 7.6cm possible in Atlanta and much higher amounts in the Carolinas.
President Barack Obama declared a disaster in South Carolina and for parts of Georgia, opening the way for federal aid. In Myrtle Beach, South Carolina, palm trees were covered with a thick crust of ice.
The storm didn't cause the widespread highway problems in Atlanta that the last storm did, largely because people had learned their lesson. Streets and highways were largely deserted.
The storm then moved northward, threatening to bring more than 30cm of snow on Thursday to the mid-Atlantic and Northeast.
Washington DC could get up to 20cm of snow. New York City could see 15cm.
Federal offices in the Washington DC area will be closed on Thursday, the government announced late Wednesday.
Ice combined with wind gusts up to 48kph snapped tree limbs and power lines. More than 200 000 homes and businesses lost electricity in Georgia, 130 000 in South Carolina and nearly 30 000 in Louisiana. Some people could be in the dark for days.
Atlanta was caught unprepared by the last storm on 28 January, when thousands of children were stranded all night in schools by less than 8cm of snow and countless drivers abandoned their cars.